Electrically shielded cap for a unit of the ignition system of internal-combustion engines



2,987 NITION mgwvw 3 Sheets-Sheet 1 June 6, 1961 s. E. ESTESELECTRICALLY SHIELDED CAP FOR A UNIT OF THE IG SYSTEM OFINTERNAL-COMBUSTION ENGINES Filed July 16, 1959 INVENTOR.

STANLEY E1 2 June 6, 1961 TES 2 %87,587

5. E. ES 9 ELECTRICALLY SHIELDED CAP FOR A UNIT OF THE IGNITIO SYSTEM OFINTERNAL-COMBUSTION ENGINES Filed July 16, 1959 3 Sheets-Sheet 2 INVENTOR.

June 6, 1961 s. E. ESTES 2,987,587

ELECTRICALLY SHIELDED CAP FOR A UNIT OF THE IGNITION SYSTEM OFINTERNAL-COMBUSTION ENGINES 3 Sheets-Sheet 3 Filed July 16, 1959 IN VENTOR.

, irroemsys United States Patent 2,987,587 ELECTRICALLY SHIELDED CAP FORA UNIT OF THE IGNITION SYSTEM OF INTERNAL-COM- BUSTION ENGINES StanleyE. Estes, Inglewood, Calif., assignor to Halle'tt Manufacturing Company,Los Angeles, Calif. a corporation of California Filed July 16, 1959,Ser. No. 827,657 4 Claims. (Cl. 200-19) This invention relates todistributors and magnetos for the electric ignition systems ofinternal-combustion engines and more particularly to a cap for suchdistributors and magnetos and to conductors by which a distributor ormagneto is connected to the spark plugs of an internal-combustionengine.

A distributor or a magneto of an internal-combustion engine emits strayelectrical fields which, if not controlled, become picked up by anyradio transmitter or receiver located close to the engine, the strayfields causing noise and disturbances in the radio equipment. Radiointerferences of that type are objectionable in motor vehicles,airplanes, ships and submarines, and in stationary installationsemploying radio equipment. Heretofore shields have been employed in theform of metal containers or boxes for enclosing the distributor or themagneto to reduce radio interference; however, such containers haveseveral substantial disadvantages.

By this invention there is provided a shield against emission of strayelectrical fields from a unit (distributor or magneto) of the electricsystem of an engine, the shield being in intimate contact with theoutside surface of the unit thereby to locate the shield in closeproximity to the source of the stray fields. According to this inventionit has been found that this can be accomplished advantageously bycoating the outer surface of the insulation cap of a distributor or of amagneto with a metal layer and providing for electrical grounding of theshield. Also by this invention the conductors or cables which connectthe distributor or the magneto to the spark plugs of an engine and, inthe case of a distributor, to the spark coil of an engine, are adaptedto be grounded to the shield and to the engine. Furthermore, theinvention results in minimizing increase in bulk of the said electricalunits, the slight increase being negligible when compared to the bulk ofthose shields which have been employed heretofore, whereby distributorsand magnetos of this invention may be disposed in a limited spacebetween engine parts and equipment under the hood of an automobile, forexample. Also, the invention may be embodied in caps for distributorsand magnetos of conventional design, requiring no redesign of caps ofthe type which are presently on the market. Furthermore, a shield ofthis invention strengthens a cap against cracking, thereby substantiallyreducing the possibility of electrical leakage.

It is a general object of this invention to provide an electrical unitfor the ignition system of an internalcombustion engine having the abovementioned advantages.

A specific object of this invention is to provide a cap for adistributor or a magneto, of the above mentioned character, which can bemanufactured easily and simply and which is rugged in construction andis eflicient and reliable in operation.

Further objects and advantages of this invention will appear during thecourse of the following part of this specification wherein the detailsof construction and mode of operation of several embodiments of theinvention are described with reference to the accompanying drawings, inwhich:

FIG. 1 is a side elevation of a distributor embodying this invention,and connected to cables of an ignition system, a portion of thedistributor and an adaptor by which one of the cables is connected tothe distributor being cut away to show parts in section;

FIG. 2 is a central vertical section through a boss portion of thedistributor cap and an adaptor and cable terminal on an enlarged scale;

FIG. 3 is an enlarged view of a boss portion, adaptor and cable ofanother embodiment according to this invention for connecting theadaptor to the boss portion;

FIG. 4 is a side elevation with parts cut away in section of a bossportion, adaptor and cable, the adaptor being of still another form;

FIGS. 5 and 6 are exploded views, each showing a boss portion andadaptor of different forms respectively, and showing a cable arranged tobe inserted into the boss portion;

FIGS. 7, 8 and 9 are side elevations on an enlarged scale and with partscut away in section, each showing a boss portion, and means forgrounding a cable, and each being of different embodiments,respectively, according to this invention;

FIG. 10 is a detail section showing another embodiment by which a cap ofthis invention may be seated upon a base portion of an electrical unit;and

FIG. 11 is a side elevation of a magneto embodying this invention, aportion thereof being cut away to show parts in section.

Referring to the drawing in greater detail, there is shown in FIG. 1 adistributor, designated generally by reference numeral 12, ofconventional shape and embodying my invention. The distributor comprisesa hollow base 13 and a hollow cap 14. The cap is adapted to receive aplurality of peripheral conductors or cables 15 for connection to sparkplugs (not shown) of an internal-combustion engine, and a conductor orcable 16 adapted to be connected to a spark coil (not shown) of theelectrical system of an internal combustion engine.

The base 13 is formed of metal and comprises a hub portion 19 forreceiving a distributor shaft 20 which serves to mount and impartrotation to a rotor 21 within the distributor. The base has acylindrical wall portion 22 ending in an upwardly facing end surface 23upon which the cap 14 is seated.

The cap is formed of a body 25 of non-conducting material, e.g. rigidplastic as, for example, Bakelite. The inside surface of the cap body isdesignated by reference numeral 26, and the outer surface of the plasticmaterial of the body is designated by numeral 27. When the cap issecured upon the top of the base, as with conventional fastener straps28, the cap and the base portion define a closed chamber 29 within thedistributor. The plastic portion of the cap is molded to form aplurality or circular towers or bosses 30 extending upwardly at the topof the cap. The distributor of the illustrated embodiment is one havingeight such bosses 30 arranged circumferentially and uniformly spacedapart around the top of the cap, and a single boss 31 disposed centrallyin the top of the cap. Only four of the circumferentially disposedbosses 30 appear in FIG. 1. The bosses 30 receive the peripheral cables15, respectively, while the central boss 31 receives the central cable16. Each of the bosses has an aperture 34 extending verticallytherethrough, each circumferential boss 30 having a contact element 35secured in its aperture to extend into the chamber 29. As the rotor 21is rotated, it will closely approach each of the contact elements 35 insucession thereby to transmit electrical impulses from an ignition coilthrough the center cable 16 and the rotor to each contact element forenergizing the spark plugs as is well known by any who understand themode of operation of a conventional distributor for a gasoline engine.

According to this invention the outer surface of the plastic bodyportion of the cap 14 is covered by an electrically conductive layer orjacket 33 to provide a shield against emission of stray electricalfields passing. out through the distributor, such stray fields resultingfrom the sparking which occurs between the rotor and the contactelements 35 and in the points (not shown) in the distributor. Also strayfields are transmitted into the distributor from the spark plugs,through the wiring 15.

In its preferred form the jacket 38 is one which is electrolyticallydeposited upon the outer surface 27 of the insulation body portion 25.An electrolytic deposit of copper, for example, may be formed upon thebody portion 25 of the cap according to the following process. The outersurface of the insulation body is first thoroughly cleaned. In the casewhere improved adhesion of the metal jacket to the insulation materialis desired, such outer surface may be sand-blasted. The insulationmaterial is then conditioned for subsequent application of a silver filmby dipping the body into a solution of stannous chloride. After rinsingas with distilled water, the insulation body is immersed in a reducingsilver solution, e.g. an aqueous solution of silver nitrate, ammoniumhydroxide and formaldehyde. The insulation body is then rinsed againwith distilled water and electroplated in a conventional manner in anacid-copper solution. A copper layer produced as above described shouldhave a minimum thickness of about .005 inch. Thicknesses up to about .03inch are contemplated.

Metals other than copper may be employed for forming the shieldingjacket 38. Jackets of silver, aluminum, brass, steel and metal alloysmay be satisfactorily employed. Also metal may be sprayed or paintedupon the outside surface of the insulation body to form the jacket 38.

It will be noted that the jacket 38, as shown best in FIG. 1, extendsover the entire outer surface of the insulation body of the cap, i.e.from around an annular end surface 43 of each circular boss 30 and 31 tocover the top portion 41 of the insulation body and the outer surface 27of a skirt portion 42. of the cap body and the outer surface of anannular lip 43 having a lower end surface 44 of the insulation body. Theinside of the lower end of the insulation body has an annular recess 45formed therein to define a shoulder 46 by which the cap rests upon therim 23 of the base 13.

In the embodiment shown in FIG. 1, the metal jacket 33 terminates in thelower end surface 44. In FIG. 10 it will be seen that the embodimentshown therein is one in which the metal jacket 38 extends upwardly at 47within annular recess 45' to cover shoulder 46 of insulation body 25'thereby to provide a relatively large contact area of electricalconnection between the metal jacket and the base of the distributor forelectrical grounding purposes.

'In the cases in which the metal jacket 38 is electrolytically depositedor sprayed upon or otherwise applied as a coating upon the outer surfaceof the insulation body, the inside of the body may be masked, as with alacquer, prior to the coating operation. The metal coated cap may beused on the distributor with its metal surface exposed, or, if desired,the jacket 38 may be painted or finished in any other suitable manner.

It is preferred that the conductors or cables 15 and 16 be of coaxialtype having an outer sheath 50 of fine Wire mesh and a core conductor51, there being an insulation layer 52 within the sheath and around thecore conductor. To provide for good electrical connection between thecore conductors 51 and the contact elements 35, each of the contactelements has a socket portion 53 which receives a contact clip 54soldered or otherwise suitably secured on the end of the core conductorof the cable.

Adaptors 56 are provided for supporting the cables upon the bosses 30 ofthe cap. In the embodiment shown in FIGS. 1 and 2, each adaptor 56 istubular and has a cylindrical neck portion 57 for encircling a cable andan enlarged skirt portion 58 for fitting tightly down over a boss. Thebosses may be of frusto-conical configuration as shown, and the skirtportions of the adaptors may likewise be of frusto-conical configurationso that as the adaptors are pressed down around the bosses they willbecome tightly wedged against the outside surface of the metal jacket 38on the bosses. If desired, the adaptor may be soldered as at 59 to themetal jacket 38.

For electrically grounding the distributor cap of the embodiment shownin FIG. 1, there is provided a conductor 61, one end 62 of which may besoldered to one of the adaptors 56 while the other end 63 thereof may beconnected to the base portion 13 or to any other electrically groundedpart of the engine.

Referring to FIG. 3, the adapter shown therein is designated byreference numeral 65, the same being seated flush over a boss 30 priorto applying the outside jacket 38'. In this instance the jacket coversthe outside surface of the skirt portion of the adaptor thus to providegood electrical connection of the adaptor to the outside jacket.

In FIG. 4 an adaptor 68, shown therein, is an elongate species, designedfor accommodating a resistor suppressor 69 or other interferencereduction devices as are quite commonly employed in association withdistributors for gasoline engines.

In FIG. 5 an adaptor 72 is shown as having an external screw thread 73for coupling with an internally threaded nut 74 upon a cable 15. Asleeve 75 having an annular flange 76 fits over and is in engagementwith the end of the metal sheath of the cable. When the end of the cableis inserted into the socket portion of a contact element 35, the flange76 will become seated upon the outer end surface 77 of the adaptor bythe nut.

In FIG. 6, there is no adaptor which is formed separately from the cap,but instead the metal jacket 38" is one which is relatively thick,permitting the end portion thereof which surrounds the upper end of aboss to have screw threads 78 formed therein for mating with a nut 74 ona cable 15.

In the embodiment shown in FIG. 7, the boss portion of the insulationbody 25' has an annular groove 81 formed around its outer surfaceproximate outer end surface 40 whereupon when the metal jacket 38 isdeposited, it, too, will have an annular groove 82 in its outsidesurface corresponding to the annular groove 81 in the outside surface ofthe boss. An adaptor -83 for this embodiment has an inside annularprojection 84 formed therein for mating with the groove 82 of the metaljacket whereby there is a good electrical connection between the adaptorand the metal jacket.

In FIG. 8 the metal sheath 50 of the cable is cut back to leave anextension portion 86 for electrical grounding purposes as by solderingthe extension upon the outside surface of the metal jacket 38, or byattaching the portion 86 to any other electrically grounded part of theengine.

In the embodiment shown in FIG. 9, a skirt portion 58 of an adaptor 90is shown as being of larger inside size than the cap boss over which theadaptor fits leaving an annular space 91 around the boss. In this casegrounding of the adaptor is efiected as with a conductor 61. Thecylindrical neck portion 57' of the adaptor is secured as with solder tothe metal sheath of the cable 15. Spacing of the adaptor from and aroundthe metal jacket 38 of the distributor cap presents a discontinuity forradiated energy, and thus suppresses such radiated energy, by means ofdeflection against the electrically grounded skirt and metal jacket.

Referring now to FIG. 11 of the drawing, the electrical unit showntherein and which embodies this invention is a magneto, designatedgenerally by reference numeral 95. The illustrated embodiment is ofconventional design for a magneto adapted to be mounted horizontally onan engine as by a flange 96 on the hollow metal base 97 of the magneto.For the purposes of this specification a description of the particularsof the details of the inside of the magneto is not needed for anunderstanding of the invention, it being enough to mention that themagneto includes an internal coil connected to a rotor which is mountedon a shaft and arranged to be electrically connected in succession tocontact elements in a cap 98 of the magneto, similarly as describedabove for the distributor.

The magneto cap 98 is formed of a body of nonconducting material, theoutside surface thereof being covered by an electrically conductivejacket 38" which serves as a shield against emission of electricalfields therefrom. Instead of the fastener straps 28 of the distributor,there are screws 100 for securing the magneto cap 98 upon the base 97 ofthe magneto. The metal jacket 38" for the magneto cap has an annularedge 102 which seats flush upon the rim of the hollow base when thescrews 100 are tightened in the base, thus providing good electricalcontact between the jacket and the base for electrical groundingpurposes.

It is to be understood that the towers or bosses 30" of the magneto capmay be of any of the alternative constructions described above for thedistributor.

While the instant invention has been shown and described herein, in whatare conceived to be the most practical and preferred embodiments, it isrecognized that departures may be made therefrom within the scope of theinvention, which is therefore not to be limited to the details disclosedherein, but is to be accorded the full scope of the claims.

What I claim is:

1. In an ignition system of an internal-combustion engine having a capof non-conducting material including a top portion and a peripheral wallportion defining a space within the cap, a plurality of spaced apartbosses extending outwardly from the top portion, a metal jacket inintimate contact with and covering the outer surfaces of the bosses andsaid top portion and said wall portion, each boss having an apertureextending axially therethrough, a contact element secured in the bossand closing the aperture and extending into said space, conductorshaving a conductive outer shield and a terminal end portion forinsertion into an aperture to be electrically connected to a contactelement, a plurality of tubular adaptors of electrically conductivematerial, each adaptor comprising a reduced neck portion circumscribinga conductor and electrically engaging the outer shield thereof, and askirt portion for circumscribing a boss, said adaptor being infrictional engagement with the outer surface of a boss and in conductivecontact with the jacket thereon, and means for electrically groundingthe jacket.

2. The combination of claim 1, in which the configuration of the outsideof the boss and that of the inside of the skirt portion arefrusto-conical whereby the adaptor may be releasably wedged tightly downover the boss.

3. The combination of claim 1, in which the skirt portion of eachadaptor fits flush around the outside surface of its respective boss andsaid metal jacket extends over the outside surface of the skirt portion.

4. The combination of claim 1, in which each boss has a detent formed inthe outside surface thereof and each adaptor has a detent formed on theinside of the skirt portion thereof for releasably mating with thedetent on the boss.

References Cited in the file of this patent UNITED STATES PATENTS2,257,781 'Bohli Oct. 7, 1941 2,323,399 Jacobi July 6, 1943 2,379,189Rupp June 26, 1945 2,574,698 Hall Nov. 13, 1951 FOREIGN PATENTS 230,902Great Britain Mar. 17, 1925 707,474 France Apr. 14, 1931

